Animation Shows How A Woman's Pelvis Morphs During Her Lifetime

MorphoLab, Anthropological Institute and Museum, University of Zurich
A computer model shows views of the female pelvis from the front (top row) and from above (bottom row) as it changes during a woman's lifetime.

Scientists have long known that the female pelvis widens and shrinks throughout a woman's lifetime -- and now, an animated model details exactly how.

These changes are most likely mediated by estrogen, and they reveal that the female pelvis is not "written in bone," as Dr. Marcia Ponce de León, senior researcher at the University of Zurich in Switzerland and a co-author of the study, told The Huffington Post on Tuesday. "Rather, its development is sensitive to hormonal change, and probably to environmental change -- because hormones are influenced by the environment."

"Pubertal rise in estrogen concentrations mediates the widening of the pelvis and the high estrogen levels during the time of highest fertility maintain the width of the pelvis," Ponce de León said. "The postmenopausal fall of estrogen concentration results in narrowing of the pelvis."

The researchers analyzed data from CT scans of 124 women and 151 men, tracking them from birth to old age. They then used that data to create computerized models of how the female and male pelvis each develop differently.

But why does a woman's pelvis get smaller when her fertility starts to decline at the onset of menopause? Researchers concluded that a narrower pelvis improves stability when a person stands and walks upright.

"We interpret this as a functional adaptation during an individual's lifetime," Ponce de León said.